Project Summary Latinos in the United States face health disparities for obesity and related medical conditions, such as cardiovascular disease and diabetes. Targeting families to promote healthy lifestyle behaviors has been identified as an effective strategy to prevent obesity. With the importance of familism (family cohesion) among Latino population, a family based intervention is especially desirable as an engaging strategy to promote behaviors that support a healthy weight status and decrease obesity related health disparities for Latinos. Emerging evidence supports the need to include and target fathers in family based lifestyle behavior interventions. However, to date primarily mothers have been reached by such efforts in the US. Health Dads Healthy Kids (HDHK) is an evidence based program developed in Australia, shown to have significant weight and behavior treatment effects for fathers and their children, compared to controls. The HDHK program is based on Social Cognitive Theory and Family Systems Theory and aims to promote increased physical activity and improved dietary intake. An important innovation in the program is that fathers and children attend together and are both targeted as agents of behavior change for each other (reciprocal reinforcement) and to participate in fun, family activities together. HDHK has several features that may appeal to Latino families: it is delivered in group sessions by a trained facilitator from the community (collectivism), and it promotes paternal role- modeling (enforces respeto), family cohesion, and engagement together in lifestyle behaviors (familism). How- ever, HDHK should be systematically culturally adapted for Latino families to ensure appropriate enrollment, engagement and promotion of desired health outcomes for Latino families, prior to further evaluation. We propose to convene a panel of Latino fathers and mothers from the community to serve as key informants; and an expert panel of researchers with experience in culturally adapting parenting interventions for Latinos, Latino lifestyle behaviors, and the influence of Latino fathers. The two panels will work with the study team (including the developer of HDHK) to systematically modify the HDHK program to culturally adapt it for Latino families following the Ecological Validity Model. They will also inform the selection of items from established item banks of food and physical activity parenting. The resulting scales will be tested among a sample of Latino fathers to establish validated scales of parenting for Latino fathers, which is expected to be a mediator of children's behavior change in HDHK, and will be needed in the future trial. The resulting Latino-HDHK will be tested for feasibility (as measured by retention, engagement, and satisfaction), in a pilot randomized controlled trial (n=40). The pilot study will include a thorough process evaluation, including exit interviews with participating Latino fathers and their co-parent (typically mothers). Once completed, this developmental study will position us to apply for a future R01 to assess the Latino-HDHK in a fully powered randomized controlled trial.